library(gcookbook)
?PlantGrowth
pg <- PlantGrowth

summary(pg)
p <- ggplot(data = pg, aes(x = pg$group, y = pg$weight)) + geom_boxplot()
p

# flip the axis / exchange the axis
p + coord_flip()

# set the limits of y axis
p + ylim(0, max(pg$weight))
p + scale_y_continuous(limits = c(0, 10), breaks = c(0,5,10))

# set the sequance of x
p + scale_x_discrete(limits = c("trt1", "ctrl", "trt2"), labels = c("Treatment1", "Control", "Treatment2")) + theme_bw() +
    theme(axis.text = element_text(family = "Helvatica",face ="italic"),axis.title = element_text(family = "Helvatica")) + xlab("Group") +ylab("Weight")